Increased renal synthesis of ammonia from glutamine in response to metabolic acidosis is an essential component of the homeostatic regulation of acid-base balance. The time course and magnitude of the adaptative changes which occur in rat kidney have been well characterized, but the regulation of this process remains undetermined. Mitochondrial phosphate-dependent glutaminase catalyzes the first reaction in renal glutamine metabolism. The objective of the proposed research is to further characterize the properties of the mitochondrial glutaminase and the process of glutamine transport in order to determine how they contribute to the regulation of renal ammoniagenesis. The specific aims include: 1. A characterization of the membrane association and orientation of the mitochondrial phosphate-dependent glutaminase. 2. The purification and membrane reconstitution of the undegraded or native form of the glutaminase. 3. An analysis of the role of dimerization in the activation of the membrane associated glutaminase. 4. A characterization of the biosynthesis and turnover of the glutaminase. 5. Isolation and characterization of the mitochondrial glutamine transporter.